With regards the repair of cartilage damage, defects in the articular surfaces of the knee joint, especially in young active individuals, are currently a focus of interest by orthopaedic surgeons. It is desirable to repair such defects in order to prevent the articular damage from spreading, thereby leading to serious degenerative changes in the joint. Such changes may result in the need for a total knee replacement which is particularly undesirable in young active individuals with a long life expectancy. If the lifetime of the implant is less than that of the patient, a revision procedure may be necessary. Preferably, such revision procedures are to be avoided, as they are considerably inconvenient to the patient and with a lower rate of success than primary procedures. Furthermore total knee revision procedures are both lengthy and very costly.
Therefore techniques are still sought to repair focal cartilage defects, particularly in young individuals to postpone, if not obviate, the need for total knee replacement. Cartilage focal defects are still, most commonly treated with microfracture technique, in which the subchondral bone plate in the defect site is pitted with a sharp pick to cause bleeding from bone marrow. This process facilitates the migration of mesenchymal progenitor cells to the defect region and subsequent tissue growth within. Although appealing because it is simple and inexpensive, the efficacy of this treatment has not been demonstrated when dealing with full thickness cartilage defects [Frisbie, D. D., Oxford, J. T., Southwood, L., Trotter, G. W., Rodkey, W. G., Steadman, J. R., Goodnight, J. L. and McIlwraith, C. W. Early events in cartilage repair after subchondral bone microfracture. Clin Orthop Relat Res, 2003. 407 215-227; Frisbie, D. D., Trotter, G. W., Powers, B. E., Rodkey, W. G., Steadman, J. R., Howard, R. D., Park, R. D. and McIlwraith, C. W. Arthroscopic subchondral bone plate microfracture technique augments healing of large chondral defects in the radial carpal bone and medial femoral condyle of horses. Vet Surg, 1999. 28(4): 242-255; Miller, B. S., Steadman, J. R., Briggs, K. K., Rodrigo, J. J. and Rodkey, W. G. Patient satisfaction and outcome after microfracture of the degenerative knee. J Knee Surg, 2004. 17(1): 13-17. Steadman, J. R., Miller, B. S., Karas, S. G., Schlegel, T. F., Briggs, K. K. and Hawkins, R. J. The microfracture technique in the treatment of full-thickness chondral lesions of the knee in National Football League players. J Knee Surg, 2003. 16(2): 83-86; Steadman, J. R., Briggs, K. K., Rodrigo, J. J., Kocher, M. S., Gill, T. J. and Rodkey, W. G. Outcomes of microfracture for traumatic chondral defects of the knee: average 11-year follow-up. Arthroscopy, 2003. 19(5): 477-484].
Two other methods for cartilage repair are used currently but not extensively as neither gives fully satisfactory results. Specifically, in Osteochondral Autogenous Transplant System (OATS), autogenous osteochondral plugs are harvested from a donor site with sound cartilage and transplanted to the recipient site(s) of the defect(s) [Hangody, L., Feczko, P., Bartha, L., Bodo, G. and Kish, G. Mosaicplasty for the treatment of articular defects of the knee and ankle Clin Orthop Relat Res, 2001. 391: (S) 328-336; Bobic, V. Autologous osteo-chondral grafts in the management of articular cartilage lesions. Orthopade, 1999. 28(1): 19-25]. This procedure is difficult, invasive and can only be applied in a limited way since it creates as many damaged sites as those intended for repair. Further, it takes some 60 to 90 minutes to complete.
The other repair method, which uses Autogenous Chondrocytes Implants (ACI), is completed in two surgical procedures [Peterson, L., Minas, T., Brittberg, M. and Lindahl, A. Treatment of osteochondritis dissecans of the knee with autologous chondrocyte transplantation: Results at two to ten years. J Bone Joint Surg Am, 2003. 85(S1): 17-24; Brittberg, M., Lindahl, A., Nilsson, A., Ohlsson, C., Isaksson, O. and Peterson, L. Treatment of deep cartilage defects in the knee with autologous chondrocyte transplantation. N Engl J Med, 1994. 331(14): 889-895].
In the first procedure, some of the patient's sound cartilage is harvested, from which the chondrocytes are isolated and expanded over a period of six weeks, after which, in a second operative procedure, they are injected back into the site of the defect. Amongst the disadvantages of the ACI treatment are: (a) the quality of the tissue resulting from this surgical intervention is dubious; (b) the procedure requires an undesirably long rehabilitation period, during which weight bearing is severely restricted with consequent muscular atrophy; (c) frequently ectopic formation of cartilage is observed, the removal of which requires a further surgical procedure; (d) the treatment is completed in two surgical procedures, the second of which can take about 2 hours; (e) the treatment costs in total is affordable by a few. Other emerging treatment (but not yet in wide use) is the one developed by Hollander and colleagues [Hollander A P, Dickinson S C, Sims T J, Brun P, Cortivo R, Kon E, Marcacci M, Zanasi S, Borrione A, De Luca C, Pavesio A, Soranzo C, Abatangelo G: Maturation of tissue engineered cartilage implanted in injured and osteoarthritic human knees. Tissue Eng 2006, 12:1787-1798], a cell based treatment, in which Chondrocytes were isolated from healthy cartilage removed at arthroscopy (presumably from the recipient). The cells were cultured for 14 days, seeded onto esterified hyaluronic acid scaffolds (Hyalograft C), and grown for a further 14 days before implantation.
Moreover, a method and apparatus for the repair of damaged cartilage is disclosed in WO 01/39694. The repair method comprises forming a narrow groove around the damaged cartilage site with the groove extending into the bone tissue underlying the cartilage. The damaged cartilage is first removed and a biocompatible fibre based replacement material is positioned at the as-formed defect site (which, being intended for repair, will interchangeably be referred to as the repair site). This replacement material is anchored in position at the bone using a retaining means in the form of a sheet-like fibrous material that either extends from (or is positioned over) the replacement material prosthetic and extends into the groove to the underlying bone. Accordingly, the replacement material is anchored in position initially by the frictional contact of the sheet-like retaining means that is wedged and crumbled within the groove. A second stage biological fixation then occurs as tissue grows into the retaining means within the groove to replace the initial mechanical anchorage.
However, in vivo preclinical trials have shown that the retaining sheet described above did not consistently retain the pad and in a number of cases moved so that the pad was dislodged from the repair site. Further, in the trials the integration of the ingrown repair tissue with the surrounding native cartilage was poor/inconsistent, and this was attributed to the presence of the outer anchorage sheet that retained the implant scaffold/pad at the repair site. Also, whilst this sheet is not of an impervious structure, it is believed that its porosity was not sufficient to allow osseous tissue ingrowth within the groove. The interposition of the anchorage sheet between the scaffold and the native cartilage and bone surrounding the defect site may have impeded migration of the repair tissue across the sheet thereby compromising the lateral integration of the implant. The partial success of these existing, known devices highlighted the need for apparatus and methods to repair damaged cartilage sites that exhibit consistently effective and patent anchorage at the repair site and maybe more conveniently implanted during any one surgical procedure, taking into account, and addressing the different demands, placed by the size, shape, and accessibility of the different potential repair sites.